coherence litmus test and data race.

Hi,

Imagine the following program:

int a,b=0

thread1:
   a=1
   [storestore]
   a=2

thread2:
    r1=a
    r2=a

It is obvious that there is a data race since the loads/stores are plain
loads and stores. My question is about the allowed behaviors in this
particular case. Do the 2 plain loads to the same address need to be
executed in order, or will any order be fine?

In terms of litmus tests: is it allowed that code with a data race can
violate the coherence litmus test.

int a,b=0

thread1:
   a=1

thread2:
   a=2

thread3:
  r1=a
  r2=a

thread4:
   r3=a
   r4=a

So could it be that we end up with r1=1, r2=2, r3=2 and r4=1.

https://repository.upenn.edu/cgi/viewcontent.cgi?article=1980&context=cis_reports

My guess at this is allowed behavior because it doesn't change the 'within
thread as if serial semantics'.

Regards,

Peter.

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